Paper exit dust shield



1962 w. H. BAUMGARTNER 3,050,171

PAPER EXIT DUST SHIELD Filed May 26, 1961 INVENTOR Wfl LLIAM H.BAUMGARTNER ATTORNEY 3,056,171 PAPER EXiT DUST SHIELD William H.Baumgartner, hicago, 111., assignor to Teretype Corporation, Skokie,llL, a corporation of Delaware Filed May 26, 1961, Ser. No. 112,883 3Claims. (Cl. 197-133) This invention relates to a dust trap for materialhandling machines and more particularly to a dust trap for materialhandling machines at the point of egressor m gress of the material fromor to the handling machine In business machines such as teletypewriters,wherein a printing operation is taking place interiorly of a coveredmachine and a paper record is exiting from the enclosed businessmachine, it is often desired to provide shield ng of the interior partsof the teletypewriter from excessive dust or dirt carried or blown inwith air that enters through openings in the cover, such as a paper exitslot. While the paper slot may be dimensioned close to the dimensions ofthe paper exiting from the teletypewriter, nevertheless the dimensionsof a slot must be somewhat larger than the dimensions of the paperexiting from the slot, to minimize the frictional drag on the paper exitng from the machine. Therefore, it is necessary to provide shieldingfrom the dust or sand borne by the air that may enter through the paperexit slot due to the lower pressure inside of the teletypewriterdeveloped by the driving motor and cooling fan for the teletypewriter.

An object of the invention is to use a Venturi effect to precipitateforeign matter out of the air entering an enclosure.

Another object of the invention is to precipitate dust or dirt from airentering a slot through which a recording medium egresses or ingressesfrom or to a business machine.

Another object of the invention is to provide a precipitation chambernear the paper exit or entrance of an enclosed business machine toprecipitate out and collect foreign matter carried by air entering thebusiness machine.

The invention features a narrow passage through which a recordingmaterial enters or leaves a recording machine adjacent to and connectedwith a larger chamber for precipitating out the foreign material.

The invention also features a vertical wall in a large chamber againstwhich the air bearing particles of solid material impinges toprecipitate out the solid matter.

The invention consists of a covered business machine having a narrowslot substantially the size of the material that egresses or ingressesthrough the narrow slot, and a large chamber which is connected to thenarrow slot and serves as a precipitation chamber for dust entering withthe air through the narrow slot at a high velocity and passing into thelarge chamber at a greatly reduced velocity, whereby the dust borne bythe air is precipitated out on the floor of the large chamber. The largechamber also has a vertical wall against which the dust-laden air willimpinge to deposit out the dust before moving upwardly over the wallinto a narrow paper channel on the other side of the large chamber.

Other features and advantages of the invention will become apparent fromthe following detailed description when considered in conjunction withthe accompanying drawing which is a side elevational view of ateletypewriter according to the present invention in which a portion ofthe cover has been broken away to give a sectional view of the dusttrap.

Referring now to the drawing there is disclosed the general outline of ateleprinter housing 10 or enclosure, as nearly dust proof as possible,encasing a conventional teleprinter for printing messages on a web orsheet of recording medium such as the paper 12, and from which protrudesthe fiamework of a keyboard 11. Manifestly, the web or recording mediumcould be any suitable reeording media such as a paper tape, magnetictape or plastic tape entering any type of business machine such astypewriter, tape punching machine or teleprinter, as the invention isnot limited to the particular type of machine or recording mediaentering or egressing from the machine.

In the teleprinter housing 10 the paper exit cover 13 is of a clearplastic material that has one portion sup.- ported on a block 14 andthat is secured near its other end to the dust cover or housing 10 by athumb screw 15. The rear portion of the paper exiting cover 13 has adownwardly curved portion 17 which ends a very slight distance above thedust cover 10 of the teleprinter. The end of the curved portion 17 ofthe paper exit .cover.13 is spaced from the adjacent surface '16 ofcover 10 by a distance only slightly exceeding the thickness of thepaper 12 passing between this downwardly curved portion 17 and theadjacent cover surface 16. In practice this dimension would range fromapproximatelyfllS to .032 inch for a sheet of paper. Of course, thepaper exit cover 13 has side walls (not shown) which enclose the paperon its sides and provide a firm seal against the entrance of dust ordirt except through the opening 18 between the curved portion 17 and thehousing '10.

The paper supply is contained inside the housing 10 in the form of aroll 26, from which the paper passes over a straightener bar 27, andunder and around a cylindrical platen 28, at which point printing uponthe paper occurs. The paper then passes over a guide lip 29, between theexit cover 13 and a flat surface 20 of the housing 10 that is slightlyelevated with respect to surface 16, and out across the surface 16.Interconnecting the lower and upper surfaces 16 and 20 is a slightlyinclined surface or baffle 19 which forms with the paper exit cover 13and the surface 16 of the teleprinter cover 119 a relatively largechamber 21 interconnecting a first restricted passage 18, defined byexit cover 13 and surface 20 of housing 10, and a second restrictedpassage 22 defined by the end of exit cover 13 and surface 16, throughwhich paper 12 passes.

In operation of the teleprinter the paper 12 will be traversing passage18, the large chamber or cavity 21 and then emerging through passage ororifice 22 or it might conceivably be entering at passage 22, traversingthe large chamber 21 and passage 18 to gain access to the interior ofhousing 10. In any event, whether the paper 12 is entering or leavingthe housing 10, it will pass through a small cross-sectional area into alarger cross-sectional area and out a small cross-sectional area.Likewise, air, perhaps dust laden, may enter only through the smallcross-sectional area of the passage or slot 22 and through the largercross-sectional area of the chamber 21 into the small cross-sectionalarea of the channel 18. The same mass of air moving into the teleprinterhousing 10 through the slot 22 will be at a higher velocity as it entersslot 22 than it will be when it traverses the large chamber 21, whichhas a greater crosssectional area than the slot 22. Thus, as the dustborne by the air enters at a high velocity through slot 22 into thechamber 21 its velocity will be greatly reduced according to thewell-known Venturi effect, and the solid matter such as dust and sandwill be precipitated out and fall to the floor of the chamber 21.Outward movement of the paper 12 and the vibrations of the machine willtend to move the solid particles along the lower surface 16 of theteleprinter cover 10 out of the machine. Also, the high velocity airentering the chamber 21 and having its velocity reduced will impingeagainst the inclined wall 19 and this will also cause the precipitationof foreign matter and act as a barrier against the move- 3 ment ofprecipitated matter into the interior of the tele printer.

Frequently the driving motors of teleprinters are provided with fans forcooling the motors, particularly when the teleprinters are enclosed inclosely fitting covers. It is within the contemplation of the presentinvention that the air forced through such a motor by a cooling fanshall be directed through a duct to an exhaust part in the housing, andthat a slot or passage 22 shall be the sole point of entrance for airdrawn by the cooling fan, thus assuring the trapping of air drawn in bythe fan as well as air forced in by wind or other external air currents.

Although only a specific embodiment of the invention is shown in thedrawing and described in the foregoing specification it will beunderstood that invention is not limited to the specific embodimentdescribed but is capable of modification and rearrangement andsubstitution of parts and elements Without departing from the spirit ofthe invention.

What is claimed is:

1. In a printer'having a dust proof cover, a dust trap comprising apaper guide plate attached to said cover and having a first portionadjacent to said dust-proof cover to form a narrow portal for the paperand any dust-laden air and a second portion spaced from said coverportion to form a dust trap for dust-laden air.

2. In a printer having an enclosing cover with stepped surfaces, a dusttrap comprising a paper guide plate having a first portion adjacent oneof the stepped surfaces of the cover to form a narrow exit for a sheetof paper and a second portion adjacent the other of the stepped surfacesbut spaced from the first of the stepped surfaces of the cover to form adust trap for dust-laden air that enters through said narrow paper exit.

3. In a teleprinter the combination of a dust proof cover having anupper paper bearing surface, a lower paper bearing surface, and asubstantially vertical wall surface interconnecting said upper and lowerpaper hearing surfaces, and a paper guide plate spaced from andcompletely enclosing on three sides the paper supported on the upper andlower bearing surfaces and having a downwardly extending wall on thefourth side to almost engage the paper resting on said lower paperbearing surface of the dust proof cover and establish in cooperationwith said surfaces an orifice for passage of the paper and a dustprecipitation cavity connected to said orifice.

References Cited in the file of this patent UNITED STATES PATENTS2,164,227 Britten June 27, 1939

